The usual commercial method of forming an enamel insulating coating on a wire is, in a continuous process, to run the wire through a solution of a resin and then to evaporate the solvent and cure the resin on the wire in a hot curing tower. The coating tends to have pinholes and other discontinuities. In order to completely cover all of the metal, it is necessary to repeat the dip and curing process several times. Moreover, the coating has to be several times as thick the insulating properties of the resin require in order to provide an electric safety margin for undercoated areas. It is also difficult at times to dry and cure the resin in the wire tower because the resins in the enamel on the wire tends to skin over before all the solvent is evaporated. This problem is magnified when a high boiling solvent is present.
Attempts to coat wires in a continuous electrophoretic process have not been sufficiently successful to be widely used commercially, usually because the coating blisters during cure.